Merge pull request #82031 from artemcm/RemovePlaceholdersInDepScanner

[Dependency Scanning] Remove obsolete placeholder module concept

include/swift-c/DependencyScan/DependencyScan.h

@@ -36,7 +36,6 @@ typedef enum {
   // SwiftInterface and SwiftSource.
   SWIFTSCAN_DEPENDENCY_INFO_SWIFT_TEXTUAL = 0,
   SWIFTSCAN_DEPENDENCY_INFO_SWIFT_BINARY = 1,
-  SWIFTSCAN_DEPENDENCY_INFO_SWIFT_PLACEHOLDER = 2,
   SWIFTSCAN_DEPENDENCY_INFO_CLANG = 3
 } swiftscan_dependency_info_kind_t;
 
@@ -310,7 +309,8 @@ swiftscan_swift_binary_detail_get_module_cache_key(
 SWIFTSCAN_PUBLIC swiftscan_string_ref_t
 swiftscan_swift_binary_detail_get_user_module_version(
     swiftscan_module_details_t details);
-//=== Swift Placeholder Module Details query APIs -------------------------===//
+
+//=== Swift Placeholder Module Details query APIs - DEPRECATED -----------===//
 
 SWIFTSCAN_PUBLIC swiftscan_string_ref_t
 swiftscan_swift_placeholder_detail_get_compiled_module_path(

include/swift/AST/DiagnosticsFrontend.def

@@ -360,14 +360,6 @@ ERROR(explicit_swift_module_map_corrupted,none,
       "explicit Swift module map from %0 is malformed",
       (StringRef))
 
-ERROR(placeholder_dependency_module_map_missing,none,
-      "cannot open Swift placeholder dependency module map from %0",
-      (StringRef))
-
-ERROR(placeholder_dependency_module_map_corrupted,none,
-      "Swift placeholder dependency module map from %0 is malformed",
-      (StringRef))
-
 ERROR(const_extract_protocol_list_input_file_missing,none,
       "cannot open constant extraction protocol list input file from %0",
       (StringRef))

include/swift/AST/ModuleDependencies.h

@@ -69,30 +69,7 @@ enum class ModuleDependencyKind : int8_t {
   Clang,
   // Used to model the translation unit's source module
   SwiftSource,
-  // Placeholder dependencies are a kind of dependencies used only by the
+  LastKind = SwiftSource + 1
-  // dependency scanner. They are swift modules that the scanner will not be
-  // able to locate in its search paths and which are the responsibility of the
-  // scanner's client to ensure are provided.
-  //
-  // Placeholder dependencies will be specified in the scanner's output
-  // dependency graph where it is the responsibility of the scanner's client to
-  // ensure required post-processing takes place to "resolve" them. In order to
-  // do so, the client (swift driver, or any other client build system) is
-  // expected to have access to a full dependency graph of all placeholder
-  // dependencies and be able to replace placeholder nodes in the dependency
-  // graph with their full dependency trees, `uniquing` common dependency module
-  // nodes in the process.
-  //
-  // One example where placeholder dependencies are employed is when using
-  // SwiftPM in Explicit Module Build mode. SwiftPM constructs a build plan for
-  // all targets ahead-of-time. When planning a build for a target that depends
-  // on other targets, the dependency scanning action is not able to locate
-  // dependency target modules, because they have not yet been built. Instead,
-  // the build system treats them as placeholder dependencies and resolves them
-  // with `actual` dependencies in a post-processing step once dependency graphs
-  // of all targets, individually, have been computed.
-  SwiftPlaceholder,
-  LastKind = SwiftPlaceholder + 1
 };
 
 /// This is used to idenfity a specific macro plugin dependency.
@@ -542,39 +519,6 @@ public:
   }
 };
 
-/// Describes an placeholder Swift module dependency module stub.
-///
-/// This class is mostly an implementation detail for \c ModuleDependencyInfo.
-
-class SwiftPlaceholderModuleDependencyStorage
-    : public ModuleDependencyInfoStorageBase {
-public:
-  SwiftPlaceholderModuleDependencyStorage(StringRef compiledModulePath,
-                                          StringRef moduleDocPath,
-                                          StringRef sourceInfoPath)
-      : ModuleDependencyInfoStorageBase(ModuleDependencyKind::SwiftPlaceholder, {}, {},
-                                        {}),
-        compiledModulePath(compiledModulePath), moduleDocPath(moduleDocPath),
-        sourceInfoPath(sourceInfoPath) {}
-
-  ModuleDependencyInfoStorageBase *clone() const override {
-    return new SwiftPlaceholderModuleDependencyStorage(*this);
-  }
-
-  /// The path to the .swiftmodule file.
-  const std::string compiledModulePath;
-
-  /// The path to the .swiftModuleDoc file.
-  const std::string moduleDocPath;
-
-  /// The path to the .swiftSourceInfo file.
-  const std::string sourceInfoPath;
-
-  static bool classof(const ModuleDependencyInfoStorageBase *base) {
-    return base->dependencyKind == ModuleDependencyKind::SwiftPlaceholder;
-  }
-};
-
 // MARK: Module Dependency Info
 /// Describes the dependencies of a given module.
 ///
@@ -675,16 +619,6 @@ public:
         CASFileSystemRootID, clangIncludeTreeRoot, moduleCacheKey, IsSystem));
   }
 
-  /// Describe a placeholder dependency swift module.
-  static ModuleDependencyInfo
-  forPlaceholderSwiftModuleStub(StringRef compiledModulePath,
-                                StringRef moduleDocPath,
-                                StringRef sourceInfoPath) {
-    return ModuleDependencyInfo(
-        std::make_unique<SwiftPlaceholderModuleDependencyStorage>(
-            compiledModulePath, moduleDocPath, sourceInfoPath));
-  }
-
   /// Retrieve the module-level imports.
   ArrayRef<ScannerImportStatementInfo> getModuleImports() const {
     return storage->moduleImports;
@@ -903,7 +837,7 @@ public:
   bool isTestableImport(StringRef moduleName) const;
 
   /// Whether the dependencies are for a Swift module: either Textual, Source,
-  /// Binary, or Placeholder.
+  /// or Binary
   bool isSwiftModule() const;
 
   /// Whether the dependencies are for a textual interface Swift module or a
@@ -919,9 +853,6 @@ public:
   /// Whether the dependencies are for a binary Swift module.
   bool isSwiftBinaryModule() const;
 
-  /// Whether this represents a placeholder module stub
-  bool isSwiftPlaceholderModule() const;
-
   /// Whether the dependencies are for a Clang module.
   bool isClangModule() const;
 
@@ -940,10 +871,6 @@ public:
   /// Retrieve the dependencies for a Clang module.
   const ClangModuleDependencyStorage *getAsClangModule() const;
 
-  /// Retrieve the dependencies for a placeholder dependency module stub.
-  const SwiftPlaceholderModuleDependencyStorage *
-  getAsPlaceholderDependencyModule() const;
-
   /// Add a dependency on the given module, if it was not already in the set.
   void
   addOptionalModuleImport(StringRef module, bool isExported,

include/swift/DependencyScan/DependencyScanImpl.h

@@ -43,7 +43,6 @@ struct swiftscan_dependency_info_s {
   /// "swiftInterface"
   /// "swiftSource"
   /// "swiftBinary"
-  /// "swiftPlaceholder"
   /// "clang""
   swiftscan_string_ref_t module_name;
 
@@ -192,19 +191,6 @@ typedef struct {
   swiftscan_string_ref_t user_module_version;
 } swiftscan_swift_binary_details_t;
 
-/// Swift placeholder modules carry additional details that specify their
-/// module doc path and source info paths.
-typedef struct {
-  /// The path to the pre-compiled binary module
-  swiftscan_string_ref_t compiled_module_path;
-
-  /// The path to the .swiftModuleDoc file.
-  swiftscan_string_ref_t module_doc_path;
-
-  /// The path to the .swiftSourceInfo file.
-  swiftscan_string_ref_t module_source_info_path;
-} swiftscan_swift_placeholder_details_t;
-
 /// Clang modules are built from a module map file.
 typedef struct {
   /// The path to the module map used to build this module.
@@ -231,7 +217,6 @@ struct swiftscan_module_details_s {
   union {
     swiftscan_swift_textual_details_t swift_textual_details;
     swiftscan_swift_binary_details_t swift_binary_details;
-    swiftscan_swift_placeholder_details_t swift_placeholder_details;
     swiftscan_clang_details_t clang_details;
   };
 };

include/swift/DependencyScan/DependencyScanningTool.h

@@ -68,14 +68,12 @@ public:
   /// Construct a dependency scanning tool.
   DependencyScanningTool();
 
-  /// Collect the full module dependency graph for the input, ignoring any
+  /// Collect the full module dependency graph for the input.
-  /// placeholder modules.
   ///
   /// \returns a \c StringError with the diagnostic output if errors
   /// occurred, \c swiftscan_dependency_result_t otherwise.
   llvm::ErrorOr<swiftscan_dependency_graph_t>
   getDependencies(ArrayRef<const char *> Command,
-                  const llvm::StringSet<> &PlaceholderModules,
                   StringRef WorkingDirectory);
 
   /// Collect the set of imports for the input module

include/swift/DependencyScan/SerializedModuleDependencyCacheFormat.h

@@ -39,7 +39,7 @@ using llvm::BCVBR;
 
 /// Every .moddepcache file begins with these 4 bytes, for easy identification.
 const unsigned char MODULE_DEPENDENCY_CACHE_FORMAT_SIGNATURE[] = {'I', 'M', 'D','C'};
-const unsigned MODULE_DEPENDENCY_CACHE_FORMAT_VERSION_MAJOR = 9;
+const unsigned MODULE_DEPENDENCY_CACHE_FORMAT_VERSION_MAJOR = 10;
 /// Increment this on every change.
 const unsigned MODULE_DEPENDENCY_CACHE_FORMAT_VERSION_MINOR = 3;
 
@@ -112,7 +112,6 @@ enum {
   OPTIONAL_IMPORT_STATEMENT_ARRAY_NODE,
   SWIFT_INTERFACE_MODULE_DETAILS_NODE,
   SWIFT_SOURCE_MODULE_DETAILS_NODE,
-  SWIFT_PLACEHOLDER_MODULE_DETAILS_NODE,
   SWIFT_BINARY_MODULE_DETAILS_NODE,
   CLANG_MODULE_DETAILS_NODE,
   IDENTIFIER_NODE,
@@ -208,7 +207,6 @@ using OptionalImportStatementArrayLayout =
 // - SwiftInterfaceModuleDetails
 // - SwiftSourceModuleDetails
 // - SwiftBinaryModuleDetails
-// - SwiftPlaceholderModuleDetails
 // - ClangModuleDetails
 using ModuleInfoLayout =
     BCRecordLayout<MODULE_NODE,                    // ID
@@ -273,13 +271,6 @@ using SwiftBinaryModuleDetailsLayout =
                    IdentifierIDField                 // UserModuleVersion
                    >;
 
-using SwiftPlaceholderModuleDetailsLayout =
-    BCRecordLayout<SWIFT_PLACEHOLDER_MODULE_DETAILS_NODE, // ID
-                   FileIDField,                           // compiledModulePath
-                   FileIDField,                           // moduleDocPath
-                   FileIDField                            // moduleSourceInfoPath
-                   >;
-
 using ClangModuleDetailsLayout =
     BCRecordLayout<CLANG_MODULE_DETAILS_NODE, // ID
                    FileIDField,               // pcmOutputPath

include/swift/Option/FrontendOptions.td

@@ -258,10 +258,6 @@ def const_gather_protocols_file
   : Separate<["-"], "const-gather-protocols-file">, MetaVarName<"<path>">,
     HelpText<"Specify a list of protocols for extraction of conformances' const values'">;
 
-def placeholder_dependency_module_map
-  : Separate<["-"], "placeholder-dependency-module-map-file">, MetaVarName<"<path>">,
-    HelpText<"Specify a JSON file containing information of external Swift module dependencies">;
-
 def import_prescan : Flag<["-"], "import-prescan">,
    HelpText<"When performing a dependency scan, only identify all imports of the main Swift module sources">;
 

include/swift/Serialization/ScanningLoaders.h

@@ -83,51 +83,6 @@ public:
     return MDS->getKind() == MDS_plain;
   }
 };
-
-/// A ModuleLoader that loads placeholder dependency module stubs specified in
-/// -placeholder-dependency-module-map-file
-/// This loader is used only in dependency scanning to inform the scanner that a
-/// set of modules constitute placeholder dependencies that are not visible to
-/// the scanner but will nevertheless be provided by the scanner's clients. This
-/// "loader" will not attempt to load any module files.
-class PlaceholderSwiftModuleScanner : public SwiftModuleScanner {
-  /// Scan the given placeholder module map
-  void parsePlaceholderModuleMap(StringRef fileName);
-
-  llvm::StringMap<ExplicitSwiftModuleInputInfo> PlaceholderDependencyModuleMap;
-  llvm::BumpPtrAllocator Allocator;
-
-public:
-  PlaceholderSwiftModuleScanner(ASTContext &ctx, ModuleLoadingMode LoadMode,
-                                Identifier moduleName,
-                                StringRef PlaceholderDependencyModuleMap,
-                                InterfaceSubContextDelegate &astDelegate,
-                                StringRef moduleOutputPath,
-                                StringRef sdkModuleOutputPath)
-      : SwiftModuleScanner(ctx, LoadMode, moduleName, astDelegate,
-                           moduleOutputPath, sdkModuleOutputPath, {},
-                           MDS_placeholder) {
-    // FIXME: Find a better place for this map to live, to avoid
-    // doing the parsing on every module.
-    if (!PlaceholderDependencyModuleMap.empty()) {
-      parsePlaceholderModuleMap(PlaceholderDependencyModuleMap);
-    }
-  }
-
-  virtual bool
-  findModule(ImportPath::Element moduleID,
-             SmallVectorImpl<char> *moduleInterfacePath,
-             SmallVectorImpl<char> *moduleInterfaceSourcePath,
-             std::unique_ptr<llvm::MemoryBuffer> *moduleBuffer,
-             std::unique_ptr<llvm::MemoryBuffer> *moduleDocBuffer,
-             std::unique_ptr<llvm::MemoryBuffer> *moduleSourceInfoBuffer,
-             bool skipBuildingInterface, bool isTestableDependencyLookup,
-             bool &isFramework, bool &isSystemModule) override;
-
-  static bool classof(const SwiftModuleScanner *MDS) {
-    return MDS->getKind() == MDS_placeholder;
-  }
-};
 } // namespace swift
 
 #endif // SWIFT_SCANNINGLOADERS_H

lib/AST/ModuleDependencies.cpp

@@ -36,7 +36,7 @@ ModuleDependencyInfoStorageBase::~ModuleDependencyInfoStorageBase() {}
 
 bool ModuleDependencyInfo::isSwiftModule() const {
   return isSwiftInterfaceModule() || isSwiftSourceModule() ||
-         isSwiftBinaryModule() || isSwiftPlaceholderModule();
+         isSwiftBinaryModule();
 }
 
 bool ModuleDependencyInfo::isTextualSwiftModule() const {
@@ -66,10 +66,6 @@ bool ModuleDependencyInfo::isSwiftBinaryModule() const {
   return isa<SwiftBinaryModuleDependencyStorage>(storage.get());
 }
 
-bool ModuleDependencyInfo::isSwiftPlaceholderModule() const {
-  return isa<SwiftPlaceholderModuleDependencyStorage>(storage.get());
-}
-
 bool ModuleDependencyInfo::isClangModule() const {
   return isa<ClangModuleDependencyStorage>(storage.get());
 }
@@ -97,12 +93,6 @@ ModuleDependencyInfo::getAsClangModule() const {
   return dyn_cast<ClangModuleDependencyStorage>(storage.get());
 }
 
-/// Retrieve the dependencies for a placeholder dependency module stub.
-const SwiftPlaceholderModuleDependencyStorage *
-ModuleDependencyInfo::getAsPlaceholderDependencyModule() const {
-  return dyn_cast<SwiftPlaceholderModuleDependencyStorage>(storage.get());
-}
-
 void ModuleDependencyInfo::addTestableImport(ImportPath::Module module) {
   assert(getAsSwiftSourceModule() && "Expected source module for addTestableImport.");
   dyn_cast<SwiftSourceModuleDependenciesStorage>(storage.get())->addTestableImport(module);
@@ -388,11 +378,6 @@ std::string ModuleDependencyInfo::getModuleOutputPath() const {
         cast<SwiftBinaryModuleDependencyStorage>(storage.get());
     return swiftBinaryStorage->compiledModulePath;
   }
-  case swift::ModuleDependencyKind::SwiftPlaceholder: {
-    auto swiftPlaceholderStorage =
-        cast<SwiftPlaceholderModuleDependencyStorage>(storage.get());
-    return swiftPlaceholderStorage->compiledModulePath;
-  }
   default:
     llvm_unreachable("Unexpected dependency kind");
   }
@@ -876,8 +861,6 @@ ModuleDependenciesCache::findSwiftDependency(StringRef moduleName) const {
     return found;
   if (auto found = findDependency(moduleName, ModuleDependencyKind::SwiftSource))
     return found;
-  if (auto found = findDependency(moduleName, ModuleDependencyKind::SwiftPlaceholder))
-    return found;
   return std::nullopt;
 }
 

lib/AST/ModuleLoader.cpp

@@ -240,9 +240,6 @@ ModuleDependencyInfo::collectCrossImportOverlayNames(
     case swift::ModuleDependencyKind::SwiftSource: {
       return result;
     }
-    case swift::ModuleDependencyKind::SwiftPlaceholder: {
-      return result;
-    }
     case swift::ModuleDependencyKind::LastKind:
       llvm_unreachable("Unhandled dependency kind.");
   }

lib/DependencyScan/DependencyScanJSON.cpp

@@ -134,7 +134,6 @@ void writeEncodedModuleIdJSONValue(llvm::raw_ostream &out,
   out << "{\n";
   static const std::string textualPrefix("swiftTextual");
   static const std::string binaryPrefix("swiftBinary");
-  static const std::string placeholderPrefix("swiftPlaceholder");
   static const std::string clangPrefix("clang");
   std::string valueStr = get_C_string(value);
   std::string moduleKind;
@@ -146,10 +145,6 @@ void writeEncodedModuleIdJSONValue(llvm::raw_ostream &out,
     // FIXME: rename to be consistent in the clients (swift-driver)
     moduleKind = "swiftPrebuiltExternal";
     moduleName = valueStr.substr(binaryPrefix.size() + 1);
-  } else if (!valueStr.compare(0, placeholderPrefix.size(),
-                               placeholderPrefix)) {
-    moduleKind = "swiftPlaceholder";
-    moduleName = valueStr.substr(placeholderPrefix.size() + 1);
   } else {
     moduleKind = "clang";
     moduleName = valueStr.substr(clangPrefix.size() + 1);
@@ -365,13 +360,6 @@ getAsTextualDependencyModule(swiftscan_module_details_t details) {
   return nullptr;
 }
 
-static const swiftscan_swift_placeholder_details_t *
-getAsPlaceholderDependencyModule(swiftscan_module_details_t details) {
-  if (details->kind == SWIFTSCAN_DEPENDENCY_INFO_SWIFT_PLACEHOLDER)
-    return &details->swift_placeholder_details;
-  return nullptr;
-}
-
 static const swiftscan_swift_binary_details_t *
 getAsBinaryDependencyModule(swiftscan_module_details_t details) {
   if (details->kind == SWIFTSCAN_DEPENDENCY_INFO_SWIFT_BINARY)
@@ -418,8 +406,6 @@ void writeJSON(llvm::raw_ostream &out,
     out << ",\n";
     out.indent(2 * 2);
     out << "{\n";
-    auto swiftPlaceholderDeps =
-        getAsPlaceholderDependencyModule(moduleInfo.details);
     auto swiftTextualDeps = getAsTextualDependencyModule(moduleInfo.details);
     auto swiftBinaryDeps = getAsBinaryDependencyModule(moduleInfo.details);
     auto clangDeps = getAsClangDependencyModule(moduleInfo.details);
@@ -432,9 +418,7 @@ void writeJSON(llvm::raw_ostream &out,
         std::string(get_C_string(moduleInfo.module_name));
     std::string moduleName =
         moduleKindAndName.substr(moduleKindAndName.find(":") + 1);
-    if (swiftPlaceholderDeps)
+    if (swiftBinaryDeps)
-      modulePath = get_C_string(swiftPlaceholderDeps->compiled_module_path);
-    else if (swiftBinaryDeps)
       modulePath = get_C_string(swiftBinaryDeps->compiled_module_path);
     else if (clangDeps || swiftTextualDeps)
       modulePath = get_C_string(moduleInfo.module_path);
@@ -590,25 +574,6 @@ void writeJSON(llvm::raw_ostream &out,
                           "swiftOverlayDependencies", 5,
                           /*trailingComma=*/false);
       }
-    } else if (swiftPlaceholderDeps) {
-      out << "\"swiftPlaceholder\": {\n";
-
-      // Module doc file
-      if (swiftPlaceholderDeps->module_doc_path.data &&
-          get_C_string(swiftPlaceholderDeps->module_doc_path)[0] != '\0')
-        writeJSONSingleField(out, "moduleDocPath",
-                             swiftPlaceholderDeps->module_doc_path,
-                             /*indentLevel=*/5,
-                             /*trailingComma=*/true);
-
-      // Module Source Info file
-      if (swiftPlaceholderDeps->module_source_info_path.data &&
-          get_C_string(swiftPlaceholderDeps->module_source_info_path)[0] !=
-              '\0')
-        writeJSONSingleField(out, "moduleSourceInfoPath",
-                             swiftPlaceholderDeps->module_source_info_path,
-                             /*indentLevel=*/5,
-                             /*trailingComma=*/false);
     } else if (swiftBinaryDeps) {
       bool hasOverlayDependencies =
         swiftBinaryDeps->swift_overlay_module_dependencies &&

lib/DependencyScan/DependencyScanningTool.cpp

@@ -271,7 +271,6 @@ DependencyScanningTool::DependencyScanningTool()
 llvm::ErrorOr<swiftscan_dependency_graph_t>
 DependencyScanningTool::getDependencies(
     ArrayRef<const char *> Command,
-    const llvm::StringSet<> &PlaceholderModules,
     StringRef WorkingDirectory) {
   // There may be errors as early as in instance initialization, so we must ensure
   // we can catch those.

lib/DependencyScan/ModuleDependencyCacheSerialization.cpp

@@ -751,34 +751,6 @@ bool ModuleDependenciesCacheDeserializer::readGraph(
       break;
     }
 
-    case SWIFT_PLACEHOLDER_MODULE_DETAILS_NODE: {
-      if (!hasCurrentModule)
-        llvm::report_fatal_error(
-            "Unexpected SWIFT_PLACEHOLDER_MODULE_DETAILS_NODE record");
-      unsigned compiledModulePathID, moduleDocPathID, moduleSourceInfoPathID;
-      SwiftPlaceholderModuleDetailsLayout::readRecord(
-          Scratch, compiledModulePathID, moduleDocPathID,
-          moduleSourceInfoPathID);
-
-      auto compiledModulePath = getIdentifier(compiledModulePathID);
-      if (!compiledModulePath)
-        llvm::report_fatal_error("Bad compiled module path");
-      auto moduleDocPath = getIdentifier(moduleDocPathID);
-      if (!moduleDocPath)
-        llvm::report_fatal_error("Bad module doc path");
-      auto moduleSourceInfoPath = getIdentifier(moduleSourceInfoPathID);
-      if (!moduleSourceInfoPath)
-        llvm::report_fatal_error("Bad module source info path");
-
-      // Form the dependencies storage object
-      auto moduleDep = ModuleDependencyInfo::forPlaceholderSwiftModuleStub(
-          *compiledModulePath, *moduleDocPath, *moduleSourceInfoPath);
-
-      cache.recordDependency(currentModuleName, std::move(moduleDep));
-      hasCurrentModule = false;
-      break;
-    }
-
     case CLANG_MODULE_DETAILS_NODE: {
       if (!hasCurrentModule)
         llvm::report_fatal_error("Unexpected CLANG_MODULE_DETAILS_NODE record");
@@ -1013,7 +985,6 @@ ModuleDependenciesCacheDeserializer::getModuleDependencyIDArray(unsigned n) {
   if (encodedIdentifierStringArray) {
     static const std::string textualPrefix("swiftTextual");
     static const std::string binaryPrefix("swiftBinary");
-    static const std::string placeholderPrefix("swiftPlaceholder");
     static const std::string clangPrefix("clang");
     std::vector<ModuleDependencyID> result;
     for (const auto &encodedIdentifierString : *encodedIdentifierStringArray) {
@@ -1028,11 +999,6 @@ ModuleDependenciesCacheDeserializer::getModuleDependencyIDArray(unsigned n) {
         auto moduleName =
             encodedIdentifierString.substr(binaryPrefix.size() + 1);
         id = {moduleName, ModuleDependencyKind::SwiftBinary};
-      } else if (!encodedIdentifierString.compare(0, placeholderPrefix.size(),
-                                                  placeholderPrefix)) {
-        auto moduleName =
-            encodedIdentifierString.substr(placeholderPrefix.size() + 1);
-        id = {moduleName, ModuleDependencyKind::SwiftPlaceholder};
       } else {
         auto moduleName =
             encodedIdentifierString.substr(clangPrefix.size() + 1);
@@ -1268,7 +1234,6 @@ void ModuleDependenciesCacheSerializer::writeBlockInfoBlock() {
   BLOCK_RECORD(graph_block, SWIFT_INTERFACE_MODULE_DETAILS_NODE);
   BLOCK_RECORD(graph_block, SWIFT_SOURCE_MODULE_DETAILS_NODE);
   BLOCK_RECORD(graph_block, SWIFT_BINARY_MODULE_DETAILS_NODE);
-  BLOCK_RECORD(graph_block, SWIFT_PLACEHOLDER_MODULE_DETAILS_NODE);
   BLOCK_RECORD(graph_block, CLANG_MODULE_DETAILS_NODE);
 }
 
@@ -1668,17 +1633,6 @@ void ModuleDependenciesCacheSerializer::writeModuleInfo(
         getIdentifier(swiftBinDeps->userModuleVersion));
     break;
   }
-  case swift::ModuleDependencyKind::SwiftPlaceholder: {
-    auto swiftPHDeps = dependencyInfo.getAsPlaceholderDependencyModule();
-    assert(swiftPHDeps);
-    SwiftPlaceholderModuleDetailsLayout::emitRecord(
-        Out, ScratchRecord,
-        AbbrCodes[SwiftPlaceholderModuleDetailsLayout::Code],
-        getIdentifier(swiftPHDeps->compiledModulePath),
-        getIdentifier(swiftPHDeps->moduleDocPath),
-        getIdentifier(swiftPHDeps->sourceInfoPath));
-    break;
-  }
   case swift::ModuleDependencyKind::Clang: {
     auto clangDeps = dependencyInfo.getAsClangModule();
     assert(clangDeps);
@@ -1936,14 +1890,6 @@ void ModuleDependenciesCacheSerializer::collectStringsAndArrays(
                        [this](auto &sp) { addIdentifier(sp.Path); });
         break;
       }
-      case swift::ModuleDependencyKind::SwiftPlaceholder: {
-        auto swiftPHDeps = dependencyInfo->getAsPlaceholderDependencyModule();
-        assert(swiftPHDeps);
-        addIdentifier(swiftPHDeps->compiledModulePath);
-        addIdentifier(swiftPHDeps->moduleDocPath);
-        addIdentifier(swiftPHDeps->sourceInfoPath);
-        break;
-      }
       case swift::ModuleDependencyKind::SwiftSource: {
         auto swiftSourceDeps = dependencyInfo->getAsSwiftSourceModule();
         assert(swiftSourceDeps);
@@ -2021,7 +1967,6 @@ void ModuleDependenciesCacheSerializer::writeInterModuleDependenciesCache(
   registerRecordAbbr<SwiftSourceModuleDetailsLayout>();
   registerRecordAbbr<SwiftInterfaceModuleDetailsLayout>();
   registerRecordAbbr<SwiftBinaryModuleDetailsLayout>();
-  registerRecordAbbr<SwiftPlaceholderModuleDetailsLayout>();
   registerRecordAbbr<ClangModuleDetailsLayout>();
 
   // Make a pass to collect all unique strings and arrays

lib/DependencyScan/ModuleDependencyScanner.cpp

@@ -104,8 +104,7 @@ findPathToDependency(ModuleDependencyID dependency,
 static bool isSwiftDependencyKind(ModuleDependencyKind Kind) {
   return Kind == ModuleDependencyKind::SwiftInterface ||
          Kind == ModuleDependencyKind::SwiftSource ||
-         Kind == ModuleDependencyKind::SwiftBinary ||
+         Kind == ModuleDependencyKind::SwiftBinary;
-         Kind == ModuleDependencyKind::SwiftPlaceholder;
 }
 
 // The Swift compiler does not have a concept of a working directory.
@@ -1371,8 +1370,7 @@ void ModuleDependencyScanner::resolveSwiftOverlayDependenciesForModule(
                                     Identifier moduleIdentifier) {
     auto moduleName = moduleIdentifier.str();
     if (cache.hasDependency(moduleName, ModuleDependencyKind::SwiftInterface) ||
-        cache.hasDependency(moduleName, ModuleDependencyKind::SwiftBinary) ||
+        cache.hasDependency(moduleName, ModuleDependencyKind::SwiftBinary))
-        cache.hasDependency(moduleName, ModuleDependencyKind::SwiftPlaceholder))
       return;
 
     auto moduleDependencies = withDependencyScanningWorker(
@@ -1713,10 +1711,6 @@ void ModuleDependencyScanner::diagnoseScannerFailure(
         moduleFilePath =
             entryNode->getAsSwiftBinaryModule()->compiledModulePath;
         break;
-      case swift::ModuleDependencyKind::SwiftPlaceholder:
-        moduleFilePath =
-            entryNode->getAsPlaceholderDependencyModule()->compiledModulePath;
-        break;
       case swift::ModuleDependencyKind::Clang:
         moduleFilePath = entryNode->getAsClangModule()->moduleMapFile;
         isClang = true;
@@ -1751,9 +1745,6 @@ static std::string getModuleDefiningPath(const ModuleDependencyInfo &info) {
   case swift::ModuleDependencyKind::SwiftBinary:
     path = info.getAsSwiftBinaryModule()->compiledModulePath;
     break;
-  case swift::ModuleDependencyKind::SwiftPlaceholder:
-    path = info.getAsPlaceholderDependencyModule()->compiledModulePath;
-    break;
   case swift::ModuleDependencyKind::Clang:
     path = info.getAsClangModule()->moduleMapFile;
     break;

lib/DependencyScan/ScanDependencies.cpp

@@ -92,10 +92,6 @@ public:
   // Resolve the dependencies for the current moduleID. Return true on error.
   bool resolve(const std::set<ModuleDependencyID> &dependencies,
                std::optional<std::set<ModuleDependencyID>> bridgingHeaderDeps) {
-    // No need to resolve dependency for placeholder.
-    if (moduleID.Kind == ModuleDependencyKind::SwiftPlaceholder)
-      return false;
-
     // If the dependency is already finalized, nothing needs to be done.
     if (resolvingDepInfo.isFinalized())
       return false;
@@ -116,13 +112,6 @@ public:
         if (handleSwiftBinaryModuleDependency(depModuleID, *binaryDepDetails))
           return true;
       } break;
-      case swift::ModuleDependencyKind::SwiftPlaceholder: {
-        auto placeholderDetails = depInfo.getAsPlaceholderDependencyModule();
-        assert(placeholderDetails && "Expected Swift Placeholder dependency.");
-        if (handleSwiftPlaceholderModuleDependency(depModuleID,
-                                                   *placeholderDetails))
-          return true;
-      } break;
       case swift::ModuleDependencyKind::Clang: {
         auto clangDepDetails = depInfo.getAsClangModule();
         assert(clangDepDetails && "Expected Clang Module dependency.");
@@ -195,9 +184,6 @@ private:
   bool finalize(ModuleDependencyInfo &depInfo,
                 const SwiftInterfaceModuleOutputPathResolution::ResultTy
                     &swiftInterfaceModuleOutputPath) {
-    if (resolvingDepInfo.isSwiftPlaceholderModule())
-      return false;
-
     if (resolvingDepInfo.isSwiftInterfaceModule())
       depInfo.setOutputPathAndHash(
           swiftInterfaceModuleOutputPath.outputPath.str().str(),
@@ -287,15 +273,6 @@ private:
     return false;
   }
 
-  bool handleSwiftPlaceholderModuleDependency(
-      ModuleDependencyID depModuleID,
-      const SwiftPlaceholderModuleDependencyStorage &placeholderDetails) {
-    if (!resolvingDepInfo.isSwiftSourceModule())
-      commandline.push_back("-swift-module-file=" + depModuleID.ModuleName +
-                            "=" + placeholderDetails.compiledModulePath);
-    return false;
-  }
-
   bool handleClangModuleDependency(
       ModuleDependencyID depModuleID,
       const ClangModuleDependencyStorage &clangDepDetails) {
@@ -721,9 +698,6 @@ static void bridgeDependencyIDs(const ArrayRef<ModuleDependencyID> dependencies,
     case ModuleDependencyKind::SwiftBinary:
       dependencyKindAndName = "swiftBinary";
       break;
-    case ModuleDependencyKind::SwiftPlaceholder:
-      dependencyKindAndName = "swiftPlaceholder";
-      break;
     case ModuleDependencyKind::Clang:
       dependencyKindAndName = "clang";
       break;
@@ -776,7 +750,6 @@ generateFullDependencyGraph(const CompilerInstance &instance,
     const auto &moduleID = allModules[i];
     auto &moduleDependencyInfo = cache.findKnownDependency(moduleID);
     // Collect all the required pieces to build a ModuleInfo
-    auto swiftPlaceholderDeps = moduleDependencyInfo.getAsPlaceholderDependencyModule();
     auto swiftTextualDeps = moduleDependencyInfo.getAsSwiftInterfaceModule();
     auto swiftSourceDeps = moduleDependencyInfo.getAsSwiftSourceModule();
     auto swiftBinaryDeps = moduleDependencyInfo.getAsSwiftBinaryModule();
@@ -788,8 +761,6 @@ generateFullDependencyGraph(const CompilerInstance &instance,
     std::string modulePath;
     if (swiftTextualDeps)
       modulePath = swiftTextualDeps->moduleOutputPath;
-    else if (swiftPlaceholderDeps)
-      modulePath = swiftPlaceholderDeps->compiledModulePath;
     else if (swiftBinaryDeps)
       modulePath = swiftBinaryDeps->compiledModulePath;
     else if (clangDeps)
@@ -904,12 +875,6 @@ generateFullDependencyGraph(const CompilerInstance &instance,
             create_clone(swiftSourceDeps->chainedBridgingHeaderPath.c_str()),
             create_clone(
                 swiftSourceDeps->chainedBridgingHeaderContent.c_str())};
-      } else if (swiftPlaceholderDeps) {
-        details->kind = SWIFTSCAN_DEPENDENCY_INFO_SWIFT_PLACEHOLDER;
-        details->swift_placeholder_details = {
-            create_clone(swiftPlaceholderDeps->compiledModulePath.c_str()),
-            create_clone(swiftPlaceholderDeps->moduleDocPath.c_str()),
-            create_clone(swiftPlaceholderDeps->sourceInfoPath.c_str())};
       } else if (swiftBinaryDeps) {
         details->kind = SWIFTSCAN_DEPENDENCY_INFO_SWIFT_BINARY;
         // Create an overlay dependencies set according to the output format
@@ -1346,8 +1311,6 @@ swift::dependencies::createEncodedModuleKindAndName(ModuleDependencyID id) {
     return "swiftTextual:" + id.ModuleName;
   case ModuleDependencyKind::SwiftBinary:
     return "swiftBinary:" + id.ModuleName;
-  case ModuleDependencyKind::SwiftPlaceholder:
-    return "swiftPlaceholder:" + id.ModuleName;
   case ModuleDependencyKind::Clang:
     return "clang:" + id.ModuleName;
   default:

lib/Driver/Driver.cpp

@@ -193,8 +193,6 @@ static void validateProfilingArgs(DiagnosticEngine &diags,
 
 static void validateDependencyScanningArgs(DiagnosticEngine &diags,
                                            const ArgList &args) {
-  const Arg *ExternalDependencyMap =
-      args.getLastArg(options::OPT_placeholder_dependency_module_map);
   const Arg *ScanDependencies = args.getLastArg(options::OPT_scan_dependencies);
   const Arg *Prescan = args.getLastArg(options::OPT_import_prescan);
 
@@ -207,11 +205,6 @@ static void validateDependencyScanningArgs(DiagnosticEngine &diags,
   const Arg *ValidatePriorCache =
       args.getLastArg(options::OPT_validate_prior_dependency_scan_cache);
 
-  if (ExternalDependencyMap && !ScanDependencies) {
-    diags.diagnose(SourceLoc(), diag::error_requirement_not_met,
-                   "-placeholder-dependency-module-map-file",
-                   "-scan-dependencies");
-  }
   if (Prescan && !ScanDependencies) {
     diags.diagnose(SourceLoc(), diag::error_requirement_not_met,
                    "-import-prescan", "-scan-dependencies");

lib/Frontend/CompilerInvocation.cpp

@@ -2441,8 +2441,6 @@ static bool ParseSearchPathArgs(SearchPathOptions &Opts, ArgList &Args,
   for (auto A: Args.filtered(OPT_candidate_module_file)) {
     Opts.CandidateCompiledModules.push_back(resolveSearchPath(A->getValue()));
   }
-  if (const Arg *A = Args.getLastArg(OPT_placeholder_dependency_module_map))
-    Opts.PlaceholderDependencyModuleMap = A->getValue();
 
   if (const Arg *A = Args.getLastArg(OPT_const_gather_protocols_file))
     Opts.ConstGatherProtocolListFilePath = A->getValue();

lib/Frontend/Frontend.cpp

@@ -899,14 +899,6 @@ bool CompilerInstance::setUpModuleLoaders() {
         FEOpts.SerializeModuleInterfaceDependencyHashes,
         FEOpts.shouldTrackSystemDependencies(),
         RequireOSSAModules_t(Invocation.getSILOptions()));
-    auto mainModuleName = Context->getIdentifier(FEOpts.ModuleName);
-    std::unique_ptr<PlaceholderSwiftModuleScanner> PSMS =
-        std::make_unique<PlaceholderSwiftModuleScanner>(
-            *Context, MLM, mainModuleName,
-            Context->SearchPathOpts.PlaceholderDependencyModuleMap, ASTDelegate,
-            getInvocation().getFrontendOptions().ExplicitModulesOutputPath,
-            getInvocation().getFrontendOptions().ExplicitSDKModulesOutputPath);
-    Context->addModuleLoader(std::move(PSMS));
   }
 
   return false;

lib/Serialization/ScanningLoaders.cpp

@@ -83,56 +83,6 @@ std::error_code SwiftModuleScanner::findModuleFilesInDirectory(
   return dependencies.getError();
 }
 
-bool PlaceholderSwiftModuleScanner::findModule(
-    ImportPath::Element moduleID, SmallVectorImpl<char> *moduleInterfacePath,
-    SmallVectorImpl<char> *moduleInterfaceSourcePath,
-    std::unique_ptr<llvm::MemoryBuffer> *moduleBuffer,
-    std::unique_ptr<llvm::MemoryBuffer> *moduleDocBuffer,
-    std::unique_ptr<llvm::MemoryBuffer> *moduleSourceInfoBuffer,
-    bool skipBuildingInterface, bool isTestableDependencyLookup,
-    bool &isFramework, bool &isSystemModule) {
-  StringRef moduleName = Ctx.getRealModuleName(moduleID.Item).str();
-  auto it = PlaceholderDependencyModuleMap.find(moduleName);
-  if (it == PlaceholderDependencyModuleMap.end()) {
-    return false;
-  }
-  auto &moduleInfo = it->getValue();
-  auto dependencies = ModuleDependencyInfo::forPlaceholderSwiftModuleStub(
-      moduleInfo.modulePath,
-      moduleInfo.moduleDocPath.has_value() ? moduleInfo.moduleDocPath.value()
-                                           : "",
-      moduleInfo.moduleSourceInfoPath.has_value()
-          ? moduleInfo.moduleSourceInfoPath.value()
-          : "");
-  this->dependencies = std::move(dependencies);
-  return true;
-}
-
-void PlaceholderSwiftModuleScanner::parsePlaceholderModuleMap(
-    StringRef fileName) {
-  ExplicitModuleMapParser parser(Allocator);
-  llvm::StringMap<ExplicitClangModuleInputInfo> ClangDependencyModuleMap;
-  llvm::StringMap<std::string> ModuleAliases;
-  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> fileBufOrErr =
-      llvm::MemoryBuffer::getFile(fileName);
-  if (!fileBufOrErr) {
-    Ctx.Diags.diagnose(SourceLoc(), diag::explicit_swift_module_map_missing,
-                       fileName);
-    return;
-  }
-  auto result = parser.parseSwiftExplicitModuleMap(
-      (*fileBufOrErr)->getMemBufferRef(), PlaceholderDependencyModuleMap,
-      ClangDependencyModuleMap, ModuleAliases);
-  if (result == std::errc::invalid_argument) {
-    Ctx.Diags.diagnose(SourceLoc(),
-                       diag::placeholder_dependency_module_map_corrupted,
-                       fileName);
-  } else if (result == std::errc::no_such_file_or_directory) {
-    Ctx.Diags.diagnose(
-        SourceLoc(), diag::placeholder_dependency_module_map_missing, fileName);
-  }
-}
-
 static std::vector<std::string> getCompiledCandidates(ASTContext &ctx,
                                                       StringRef moduleName,
                                                       StringRef interfacePath) {
@@ -297,36 +247,20 @@ ModuleDependencyVector SerializedModuleLoaderBase::getModuleDependencies(
   auto modulePath = builder.get();
   auto moduleId = modulePath.front().Item;
 
-  // Instantiate dependency scanning "loaders".
+  auto scanner = std::make_unique<SwiftModuleScanner>(
-  SmallVector<std::unique_ptr<SwiftModuleScanner>, 2> scanners;
-  // Placeholder dependencies must be resolved first, to prevent the
-  // ModuleDependencyScanner from first discovering artifacts of a previous
-  // build. Such artifacts are captured as compiledModuleCandidates in the
-  // dependency graph of the placeholder dependency module itself.
-  // FIXME: submodules?
-  scanners.push_back(std::make_unique<PlaceholderSwiftModuleScanner>(
-      Ctx, LoadMode, moduleId, Ctx.SearchPathOpts.PlaceholderDependencyModuleMap,
-      delegate, moduleOutputPath, sdkModuleOutputPath));
-  scanners.push_back(std::make_unique<SwiftModuleScanner>(
       Ctx, LoadMode, moduleId, delegate, moduleOutputPath, sdkModuleOutputPath,
-      swiftModuleClangCC1CommandLineArgs,
+      swiftModuleClangCC1CommandLineArgs, SwiftModuleScanner::MDS_plain);
-      SwiftModuleScanner::MDS_plain));
 
   // Check whether there is a module with this name that we can import.
-  assert(isa<PlaceholderSwiftModuleScanner>(scanners[0].get()) &&
+  if (scanner->canImportModule(modulePath, SourceLoc(), nullptr,
-         "Expected PlaceholderSwiftModuleScanner as the first dependency "
+                               isTestableDependencyLookup)) {
-         "scanner loader.");
-  for (auto &scanner : scanners) {
-    if (scanner->canImportModule(modulePath, SourceLoc(), nullptr,
-                                 isTestableDependencyLookup)) {
 
-      ModuleDependencyVector moduleDependnecies;
+    ModuleDependencyVector moduleDependnecies;
-      moduleDependnecies.push_back(
+    moduleDependnecies.push_back(
-          std::make_pair(ModuleDependencyID{moduleName.str().str(),
+        std::make_pair(ModuleDependencyID{moduleName.str().str(),
-                                            scanner->dependencies->getKind()},
+                                          scanner->dependencies->getKind()},
-                         *(scanner->dependencies)));
+                       *(scanner->dependencies)));
-      return moduleDependnecies;
+    return moduleDependnecies;
-    }
   }
 
   return {};

lib/Tooling/libSwiftScan/libSwiftScan.cpp

@@ -93,14 +93,6 @@ void swiftscan_dependency_info_details_dispose(
     swiftscan_string_dispose(
         details_impl->swift_binary_details.user_module_version);
     break;
-  case SWIFTSCAN_DEPENDENCY_INFO_SWIFT_PLACEHOLDER:
-    swiftscan_string_dispose(
-        details_impl->swift_placeholder_details.compiled_module_path);
-    swiftscan_string_dispose(
-        details_impl->swift_placeholder_details.module_doc_path);
-    swiftscan_string_dispose(
-        details_impl->swift_placeholder_details.module_source_info_path);
-    break;
   case SWIFTSCAN_DEPENDENCY_INFO_CLANG:
     swiftscan_string_dispose(details_impl->clang_details.module_map_path);
     swiftscan_string_dispose(details_impl->clang_details.context_hash);
@@ -168,7 +160,7 @@ swiftscan_dependency_graph_create(swiftscan_scanner_t scanner,
 
   // Execute the scan and bridge the result
   auto ScanResult = ScanningTool->getDependencies(
-      Compilation, {},
+      Compilation,
       swift::c_string_utils::get_C_string(invocation->working_directory));
   if (ScanResult.getError())
     return nullptr;
@@ -433,23 +425,23 @@ swiftscan_swift_binary_detail_get_user_module_version(
   return details->swift_binary_details.user_module_version;
 }
 
-//=== Swift Placeholder Module Details query APIs -------------------------===//
+//=== Swift Placeholder Module Details query APIs - DEPRECATED -----------===//
 
 swiftscan_string_ref_t
 swiftscan_swift_placeholder_detail_get_compiled_module_path(
     swiftscan_module_details_t details) {
-  return details->swift_placeholder_details.module_source_info_path;
+  return swift::c_string_utils::create_null();
 }
 
 swiftscan_string_ref_t swiftscan_swift_placeholder_detail_get_module_doc_path(
     swiftscan_module_details_t details) {
-  return details->swift_placeholder_details.module_source_info_path;
+  return swift::c_string_utils::create_null();
 }
 
 swiftscan_string_ref_t
 swiftscan_swift_placeholder_detail_get_module_source_info_path(
     swiftscan_module_details_t details) {
-  return details->swift_placeholder_details.module_source_info_path;
+  return swift::c_string_utils::create_null();
 }
 
 //=== Clang Module Details query APIs -------------------------------------===//

test/ScanDependencies/Inputs/ModuleDependencyGraph.swift

@@ -13,14 +13,12 @@ import Foundation
 
 enum ModuleDependencyId: Hashable {
   case swift(String)
-  case swiftPlaceholder(String)
   case swiftPrebuiltExternal(String)
   case clang(String)
 
   var moduleName: String {
     switch self {
     case .swift(let name): return name
-    case .swiftPlaceholder(let name): return name
     case .swiftPrebuiltExternal(let name): return name
     case .clang(let name): return name
     }
@@ -30,7 +28,6 @@ enum ModuleDependencyId: Hashable {
 extension ModuleDependencyId: Codable {
   enum CodingKeys: CodingKey {
     case swift
-    case swiftPlaceholder
     case swiftPrebuiltExternal
     case clang
   }
@@ -42,16 +39,11 @@ extension ModuleDependencyId: Codable {
       self = .swift(moduleName)
     } catch {
       do {
-        let moduleName =  try container.decode(String.self, forKey: .swiftPlaceholder)
+        let moduleName =  try container.decode(String.self, forKey: .swiftPrebuiltExternal)
-        self = .swiftPlaceholder(moduleName)
+        self = .swiftPrebuiltExternal(moduleName)
       } catch {
-        do {
+        let moduleName =  try container.decode(String.self, forKey: .clang)
-          let moduleName =  try container.decode(String.self, forKey: .swiftPrebuiltExternal)
+        self = .clang(moduleName)
-          self = .swiftPrebuiltExternal(moduleName)
-        } catch {
-          let moduleName =  try container.decode(String.self, forKey: .clang)
-          self = .clang(moduleName)
-        }
       }
     }
   }
@@ -61,8 +53,6 @@ extension ModuleDependencyId: Codable {
     switch self {
       case .swift(let moduleName):
         try container.encode(moduleName, forKey: .swift)
-      case .swiftPlaceholder(let moduleName):
-        try container.encode(moduleName, forKey: .swiftPlaceholder)
       case .swiftPrebuiltExternal(let moduleName):
         try container.encode(moduleName, forKey: .swiftPrebuiltExternal)
       case .clang(let moduleName):
@@ -99,15 +89,6 @@ struct SwiftModuleDetails: Codable {
   var swiftOverlayDependencies: [ModuleDependencyId]?
 }
 
-/// Details specific to Swift placeholder dependencies.
-struct SwiftPlaceholderModuleDetails: Codable {
-  /// The path to the .swiftModuleDoc file.
-  var moduleDocPath: String?
-
-  /// The path to the .swiftSourceInfo file.
-  var moduleSourceInfoPath: String?
-}
-
 /// Details specific to Swift externally-pre-built modules.
 struct SwiftPrebuiltExternalModuleDetails: Codable {
   /// The path to the already-compiled module that must be used instead of
@@ -152,10 +133,6 @@ struct ModuleInfo: Codable {
     /// a bridging header.
     case swift(SwiftModuleDetails)
 
-    /// Swift placeholder modules carry additional details that specify their
-    /// module doc path and source info paths.
-    case swiftPlaceholder(SwiftPlaceholderModuleDetails)
-
     /// Swift externally-prebuilt modules must communicate the path to pre-built binary artifacts
     case swiftPrebuiltExternal(SwiftPrebuiltExternalModuleDetails)
 
@@ -167,7 +144,6 @@ struct ModuleInfo: Codable {
 extension ModuleInfo.Details: Codable {
   enum CodingKeys: CodingKey {
     case swift
-    case swiftPlaceholder
     case swiftPrebuiltExternal
     case clang
   }
@@ -179,18 +155,12 @@ extension ModuleInfo.Details: Codable {
       self = .swift(details)
     } catch {
       do {
-        let details = try container.decode(SwiftPlaceholderModuleDetails.self,
+        let details = try container.decode(SwiftPrebuiltExternalModuleDetails.self,
-                                           forKey: .swiftPlaceholder)
+                                           forKey: .swiftPrebuiltExternal)
-        self = .swiftPlaceholder(details)
+        self = .swiftPrebuiltExternal(details)
       } catch {
-        do {
+        let details = try container.decode(ClangModuleDetails.self, forKey: .clang)
-          let details = try container.decode(SwiftPrebuiltExternalModuleDetails.self,
+        self = .clang(details)
-                                             forKey: .swiftPrebuiltExternal)
-          self = .swiftPrebuiltExternal(details)
-        } catch {
-          let details = try container.decode(ClangModuleDetails.self, forKey: .clang)
-          self = .clang(details)
-        }
       }
     }
   }
@@ -200,8 +170,6 @@ extension ModuleInfo.Details: Codable {
     switch self {
       case .swift(let details):
         try container.encode(details, forKey: .swift)
-      case .swiftPlaceholder(let details):
-        try container.encode(details, forKey: .swiftPlaceholder)
       case .swiftPrebuiltExternal(let details):
         try container.encode(details, forKey: .swiftPrebuiltExternal)
       case .clang(let details):

test/ScanDependencies/can_import_placeholder.swift

@@ -1,42 +0,0 @@
-// RUN: %empty-directory(%t)
-// RUN: mkdir -p %t/clang-module-cache
-// RUN: mkdir -p %t/inputs
-
-// RUN: echo "[{" > %/t/inputs/map.json
-// RUN: echo "\"moduleName\": \"SomeExternalModule\"," >> %/t/inputs/map.json
-// RUN: echo "\"modulePath\": \"%/t/inputs/SomeExternalModule.swiftmodule\"," >> %/t/inputs/map.json
-// RUN: echo "\"docPath\": \"%/t/inputs/SomeExternalModule.swiftdoc\"," >> %/t/inputs/map.json
-// RUN: echo "\"sourceInfoPath\": \"%/t/inputs/SomeExternalModule.swiftsourceinfo\"," >> %/t/inputs/map.json
-// RUN: echo "\"isFramework\": false" >> %/t/inputs/map.json
-// RUN: echo "}]" >> %/t/inputs/map.json
-
-// RUN: %target-swift-frontend -scan-dependencies -module-load-mode prefer-interface -module-cache-path %t/clang-module-cache %s -placeholder-dependency-module-map-file %t/inputs/map.json -o %t/deps.json -I %S/Inputs/CHeaders -I %S/Inputs/Swift -emit-dependencies -emit-dependencies-path %t/deps.d -import-objc-header %S/Inputs/CHeaders/Bridging.h -swift-version 4
-// RUN: %validate-json %t/deps.json | %FileCheck %s
-
-// Ensure that round-trip serialization does not affect result
-// RUN: %target-swift-frontend -scan-dependencies -module-load-mode prefer-interface -test-dependency-scan-cache-serialization -module-cache-path %t/clang-module-cache %s -placeholder-dependency-module-map-file %t/inputs/map.json -o %t/deps.json -I %S/Inputs/CHeaders -I %S/Inputs/Swift -emit-dependencies -emit-dependencies-path %t/deps.d -import-objc-header %S/Inputs/CHeaders/Bridging.h -swift-version 4
-// RUN: %validate-json %t/deps.json | %FileCheck %s
-
-// REQUIRES: executable_test
-// REQUIRES: objc_interop
-#if canImport(SomeExternalModule)
-import SomeExternalModule
-#endif
-
-// CHECK: "mainModuleName": "deps"
-
-/// --------Main module
-// CHECK-LABEL: "modulePath": "deps.swiftmodule",
-// CHECK-NEXT: sourceFiles
-// CHECK-NEXT: can_import_placeholder.swift
-
-// CHECK: directDependencies
-// CHECK-NEXT: {
-// CHECK-DAG: "swift": "F"
-// CHECK-DAG: "swiftPlaceholder": "SomeExternalModule"
-// CHECK-DAG: "swift": "Swift"
-// CHECK-DAG: "swift": "SwiftOnoneSupport"
-// CHECK-DAG: "swift": "_Concurrency"
-// CHECK-DAG: "swift": "_StringProcessing"
-// CHECK-DAG: "clang": "_SwiftConcurrencyShims"
-// CHECK: ],

test/ScanDependencies/module_deps_external.swift

@@ -1,96 +0,0 @@
-// RUN: %empty-directory(%t)
-// RUN: mkdir -p %t/clang-module-cache
-// RUN: mkdir -p %t/inputs
-
-// RUN: echo "[{" > %/t/inputs/map.json
-// RUN: echo "\"moduleName\": \"SomeExternalModule\"," >> %/t/inputs/map.json
-// RUN: echo "\"modulePath\": \"%/t/inputs/SomeExternalModule.swiftmodule\"," >> %/t/inputs/map.json
-// RUN: echo "\"docPath\": \"%/t/inputs/SomeExternalModule.swiftdoc\"," >> %/t/inputs/map.json
-// RUN: echo "\"sourceInfoPath\": \"%/t/inputs/SomeExternalModule.swiftsourceinfo\"," >> %/t/inputs/map.json
-// RUN: echo "\"isFramework\": false" >> %/t/inputs/map.json
-// RUN: echo "}]" >> %/t/inputs/map.json
-
-// RUN: %target-swift-frontend -scan-dependencies -module-load-mode prefer-interface -module-cache-path %t/clang-module-cache %s -placeholder-dependency-module-map-file %t/inputs/map.json -o %t/deps.json -I %S/Inputs/CHeaders -I %S/Inputs/Swift -emit-dependencies -emit-dependencies-path %t/deps.d -import-objc-header %S/Inputs/CHeaders/Bridging.h -swift-version 4
-
-// Check the contents of the JSON output
-// RUN: %validate-json %t/deps.json | %FileCheck %s
-
-// Check the make-style dependencies file
-// RUN: %FileCheck %s -check-prefix CHECK-MAKE-DEPS < %t/deps.d
-
-// Check that the JSON parses correctly into the canonical Swift data
-// structures.
-
-// RUN: mkdir -p %t/PrintGraph
-// RUN: cp %S/Inputs/PrintGraph.swift %t/main.swift
-// RUN: %target-build-swift %S/Inputs/ModuleDependencyGraph.swift %t/main.swift -o %t/main
-// RUN: %target-codesign %t/main
-// RUN: %target-run %t/main %t/deps.json
-
-// Ensure that round-trip serialization does not affect result
-// RUN: %target-swift-frontend -scan-dependencies -module-load-mode prefer-interface -test-dependency-scan-cache-serialization -module-cache-path %t/clang-module-cache %s -placeholder-dependency-module-map-file %t/inputs/map.json -o %t/deps.json -I %S/Inputs/CHeaders -I %S/Inputs/Swift -import-objc-header %S/Inputs/CHeaders/Bridging.h -swift-version 4
-// RUN: %validate-json %t/deps.json | %FileCheck %s
-
-// REQUIRES: executable_test
-// REQUIRES: objc_interop
-import SomeExternalModule
-
-// CHECK: "mainModuleName": "deps"
-
-/// --------Main module
-// CHECK-LABEL: "modulePath": "deps.swiftmodule",
-// CHECK-NEXT: sourceFiles
-// CHECK-NEXT: module_deps_external.swift
-
-// CHECK: directDependencies
-// CHECK-NEXT: {
-// CHECK-DAG: "clang": "F"
-// CHECK-DAG: "swiftPlaceholder": "SomeExternalModule"
-// CHECK-DAG: "swift": "Swift"
-// CHECK-DAG: "swift": "SwiftOnoneSupport"
-// CHECK-DAG: "swift": "_Concurrency"
-// CHECK-DAG: "swift": "_StringProcessing"
-// CHECK-DAG: "clang": "_SwiftConcurrencyShims"
-// CHECK: ],
-
-// CHECK: "bridgingHeader":
-// CHECK-NEXT: "path":
-// CHECK-SAME: Bridging.h
-
-// CHECK-NEXT: "sourceFiles":
-// CHECK-NEXT: Bridging.h
-// CHECK-NEXT: BridgingOther.h
-
-// CHECK:       "moduleDependencies": [
-// CHECK-NEXT:     "F"
-// CHECK-NEXT:  ],
-
-// CHECK:       "swiftOverlayDependencies": [
-// CHECK-NEXT:    {
-// CHECK-NEXT:      "swift": "F"
-// CHECK-NEXT:    }
-// CHECK-NEXT:  ]
-
-/// --------Swift external module SomeExternalModule
-// CHECK-LABEL: "modulePath": "{{.*}}{{/|\\}}SomeExternalModule.swiftmodule",
-// CHECK-NEXT: "details": {
-// CHECK-NEXT: "swiftPlaceholder": {
-// CHECK-NEXT: "moduleDocPath": "BUILD_DIR/{{.*}}/ScanDependencies/Output/module_deps_external.swift.tmp/inputs/SomeExternalModule.swiftdoc",
-// CHECK-NEXT: "moduleSourceInfoPath": "BUILD_DIR/{{.*}}/ScanDependencies/Output/module_deps_external.swift.tmp/inputs/SomeExternalModule.swiftsourceinfo"
-
-/// --------Swift module Swift
-// CHECK-LABEL: "modulePath": "{{.*}}{{/|\\}}Swift-{{.*}}.swiftmodule",
-
-// CHECK: directDependencies
-// CHECK-NEXT: {
-// CHECK-NEXT: "clang": "SwiftShims"
-
-/// --------Clang module SwiftShims
-// CHECK-LABEL: "modulePath": "{{.*}}/SwiftShims-{{.*}}.pcm",
-
-// Check make-style dependencies
-// CHECK-MAKE-DEPS: module_deps_external.swift
-// CHECK-MAKE-DEPS-SAME: Bridging.h
-// CHECK-MAKE-DEPS-SAME: BridgingOther.h
-// CHECK-MAKE-DEPS-SAME: module.modulemap
-

test/ScanDependencies/placholder_overlay_deps.swift

@@ -1,31 +0,0 @@
-// RUN: %empty-directory(%t)
-// RUN: mkdir -p %t/clang-module-cache
-// RUN: mkdir -p %t/inputs
-
-// RUN: echo "[{" > %/t/inputs/map.json
-// RUN: echo "\"moduleName\": \"Darwin\"," >> %/t/inputs/map.json
-// RUN: echo "\"modulePath\": \"%/t/inputs/Darwin.swiftmodule\"," >> %/t/inputs/map.json
-// RUN: echo "\"docPath\": \"%/t/inputs/Darwin.swiftdoc\"," >> %/t/inputs/map.json
-// RUN: echo "\"sourceInfoPath\": \"%/t/inputs/Darwin.swiftsourceinfo\"," >> %/t/inputs/map.json
-// RUN: echo "\"isFramework\": false," >> %/t/inputs/map.json
-// RUN: echo "\"isSystem\": true" >> %/t/inputs/map.json
-// RUN: echo "}]" >> %/t/inputs/map.json
-
-// RUN: %target-swift-frontend -scan-dependencies -module-cache-path %t/clang-module-cache %s -placeholder-dependency-module-map-file %t/inputs/map.json -o %t/deps.json
-
-// Check the contents of the JSON output
-// RUN: %validate-json %t/deps.json > %t/validated_deps.json
-// RUN: %FileCheck %s < %t/validated_deps.json
-
-// REQUIRES: executable_test
-// REQUIRES: objc_interop
-// REQUIRES: OS=macosx
-import Metal
-
-// Ensure the dependency on Darwin is captured even though it is a placeholder
-
-// CHECK:   "modulePath": "{{.*}}{{/|\\}}Metal-{{.*}}.swiftmodule",
-// CHECK:   "directDependencies": [
-// CHECK:     {
-// CHECK:       "swiftPlaceholder": "Darwin"
-// CHECK:     },

unittests/DependencyScan/ModuleDeps.cpp

@@ -175,7 +175,7 @@ export *\n\
   for (auto &command : CommandStrArr) {
     Command.push_back(command.c_str());
   }
-  auto DependenciesOrErr = ScannerTool.getDependencies(Command, {}, {});
+  auto DependenciesOrErr = ScannerTool.getDependencies(Command, {});
   ASSERT_FALSE(DependenciesOrErr.getError());
   auto Dependencies = DependenciesOrErr.get();
   // TODO: Output/verify dependency graph correctness
@@ -309,7 +309,7 @@ public func funcB() { }\n"));
 
   auto ScanDiagnosticConsumer = std::make_shared<DependencyScanDiagnosticCollector>();
 
-  auto DependenciesOrErr = ScannerTool.getDependencies(Command, {}, {});
+  auto DependenciesOrErr = ScannerTool.getDependencies(Command, {});
 
   // Ensure a hollow output with diagnostic info is produced
   ASSERT_FALSE(DependenciesOrErr.getError());